With increases in the average individual lifespan due to medical and scientific advances, a major challenge to society and the medical community is improving the daily lives of older individuals and extending their independence as long as possible. As a person ages, individual sensory abilities typically decline and result in poorer perception, response time, balance and memory. Research on multisensory perception indicates that older adults gain more from cross-modal stimuli compared to younger individuals, and further, compensatory strategies utilizing multisensory stimuli provide beneficial assistance to older individuals experiencing the natural decline in unisensory abilities. In order to develop effective multisensory interventions that could be clinically effective for older adults, a better understanding of the mechanisms by which multisensory integration is enhanced in this population is needed. To do this, behavioral and brain imaging experiments proposed here are designed to investigate whether increased multisensory integration in older adults is related to differences in specific stimulus driven perception (i.e., unisensory resolution) or to changes in the neural substrate underlying multisensory processing (e.g. signal to noise changes, atrophy). The specific aims of the project are as follows: 1) ln young (18-34 years old) and older (65-90 years old) individuals, assess multisensory behavioral gains in accuracy utilizing unisensory stimuli equally perceived in both age groups (normalized for age-related sensory decline) and stimuli of specific intensity (typically perceived better in young than old);2) Use functional magnetic resonance imaging (fMRI) to measure the neural correlates of increased multisensory integration in older adults considering known unisensory declines;and 3) Evaluate the relationship between age-related changes in grey matter volume and the unisensory and multisensory blood oxygenation level dependent (BOLD) response. This work will provide a better idea of why older adults more often than younger adults put information together from their five sensory systems. In some cases when the senses report the same information, this can help speed responses in older adults, but when the information is not the same between the senses, older adults have more problems than younger adults. This increased interference from other senses could lead to falls, memory difficulties, and frustration in older adults. Taking the information gained by this proposal, older adults can be given new techniques for maintaining their day to day activity level within the community by maximizing the benefits of this sensory cross-talk.